To facilitate communications in a wireless system or communications network, it is desirable to provide a plurality of wireless access and routing points (WARPs) or nodes among which communications can take place via wireless links, the nodes optionally communicating via one or more wired connection paths with a communications network, with wireless terminals communicating with the nodes also via wireless links. For clarity herein, the wireless links via which the wireless terminals communicate with the nodes are referred to as access links, and the wireless links for communications among the nodes are referred to as transit links.
In such a wireless system, for example, the nodes can be distributed within a geographical region or area within which wireless access services are to be provided, and the wireless terminals can communicate among themselves and/or with the network via the various nodes. The wireless terminals can have any of various forms, and the communicated signals can comprise any desired form of information. Such a wireless system conveniently operates in a packet communications mode, in which for example a node is only active (transmitting or receiving radio signals) when it is sending or receiving data packets, and is otherwise in a quiescent or quiet state in which it only listens for traffic and occasionally exchanges signalling messages for administration of the wireless system.
By way of example, the wireless communications via the access and transit links can be in accordance with known standards, such as the IEEE 802.11 standard for wireless LAN (local area network) communications. Conveniently channels in different frequency bands are used for the access and transit links; for example channels in the 2.4 GHz band (IEEE 802.11b) for the access links and channels in the 5.2 and 5.7 GHz bands (IEEE 802.11a) for the transit links. However, this need not be the case and the access and transit links can use other frequency bands and/or can both use the same frequency band.
Such a system desirably provides multiple beams using directional antennas, i.e. directive wireless communication paths, for at least some of the transit links between pairs of nodes, thereby facilitating re-use of channel frequencies on the transit links. In particular, directional antenna beams can provide increased gain, and hence greater range, and directional azimuth beam patterning, which attenuates unwanted co-channel and adjacent channel interference, for example arising from simultaneous transmissions over a plurality of transit links. Each node can provide any desired number and configuration of directional antenna beams and the individual beams of each node can be similar to or different from one another. Conveniently, all of the nodes are similar to one another and all of the beams of each node are similar to one another; for example each node may provide 3, 6, 8, or more similar beams, but any other (smaller or larger) number of beams may be provided.
A known way of designing such a wireless system uses laborious centralized planning to address issues such as frequency re-use, scalability (expansion or contraction) of the system over time, and adaptability to changes. With a rigid frequency re-use plan, the system must be redesigned when the interference environment changes; this is a particular problem for a system operating in an unlicensed frequency band, and is costly in terms of both labour and system capacity. If the system needs to be expanded or modified, for example to provide additional nodes, a system with centralized planning again requires massive redesign.
It would be desirable to provide an improved wireless system which is self-organizing or self-adapting as nodes are added and/or removed and/or in dependence upon changes in the environment of the system.